Purpose: The goal of this work was to determine influence of fillers on viscosity, especially of six mixtures that contain different amount of ferrite powder. It was made in order to find out an effect of introduced ferrite powder on epoxy resin processing conditions and parameters. Additionally viscosity of pure epoxy resin was determined for reference purposes. The influence of temperature on composites viscosity was also examined. Design/methodology/approach: Viscosity of mixtures based on epoxy resin that contain ferrite powders and pure epoxy resin using Hoeppler viscometer was measured. Procedures of viscosity measurements were performed for three temperatures and for three filler contents. Findings: Higher temperature of measurement resulted in lower values of viscosity while higher quantity of ferrite powder increased viscosity of mixtures. There was no difference between results of viscosity that were obtained for barium ferrite and strontium ferrite. Research limitations/implications: The main problem of this work was limitations of research method. Mixtures before measurement had to be put to the vacuum venting in order to remove air bubbles that were introduced through mixing. Also an amount of powder introduced into the matrix was limited because for higher contents it was not possible to pour mixtures into glass pipe of measurement device. Practical implications: Applied method allowed to determine the influence of temperature, kind and quantity of filler on viscosity. Viscosity is the main factor defining processing parameters in many processing technologies. Originality/value: Results of viscosity for searched composites are not known up till now. Achieved results are planned in order to use them in future works of authors on polymeric magnetic composites.